The deadly crash of a Nigerian passenger plane is renewing concerns about aviation safety in the country and the rest of West Africa.

Authorities say at least 157 people, including four on the ground, were killed when the Dana Airlines flight plowed into a Lagos residential neighborhood on Sunday.

Nigeria's Aviation Ministry said Tuesday that it had suspended the license of Dana airlines as it investigates the cause of Sunday's crash. Search crews have recovered the plane's flight data and cockpit voice recorders which may shed light on the cause of the crash. Aviation officials say the pilot reported engine trouble as he approached the Lagos airport.

William Voss, the head of the U.S.-based Flight Safety Foundation, says aviation safety, in general, is on a "multi-decade trend toward improvement." But, in a VOA interview, he said there is still a "substantial gap" in airline safety between developed and emerging nations.

He says there is a "tendency" in many African countries not to have strong implementation of international aviation standards. However, he says Nigeria had actually improved its air safety record after a string of crashes.

"They had a series of tragedies in 2005 and 2006 which really drove the top leadership in their country to action. They did all the right things and actually enjoyed a spectacular safety record over the past six years until just this past weekend," he said.

A 2005 crash of a Nigerian Bellview Airlines jet in Lagos left 117 people dead. Later that year, a Nigerian Sololiso flight crashed in Port Harcourt, killing 106 people including at least 50 school children.

A pair of crashes the following year killed a total of more than 100 people.

Voss says the likelihood of a plane crash is higher in Africa than in most regions of the world. "In Africa, it's a little difficult to quantify because there are so few flights there, the numbers jump up and down a lot. But, you're anywhere from seven, ten times more likely to be involved in an accident flying in African than you are in North America or the rest of the world," he said.

Ibrahim Mamman, a pilot with the privately owned IRS airlines in Nigeria, tells VOA that aircraft maintenance has been an ongoing issue. "The issue there is the engineers need to be trained. They need training and training and training, training all the time," he said.

Torrential rain and strong winds slowed recovery efforts at the site of the Dana Airlines crash on Tuesday.

Search crews looking for victims had been using cranes to remove the plane's twisted wreckage and debris from charred buildings.

Anxious family members of victims crowed into a Lagos hospital, on Tuesday, where they awaited word on the identities of victims.

Mallam Sair Said says he is grieving the loss of his brother, who was on the flight. "Since the incident there is no day, no moment I don't feel him around me. Anything I do, I feel as if I were going to share it with him but unfortunately I'll never share anything with him again," he said.

Aviation officials say an undetermined number of foreigners were on the flight, including Chinese nationals, U.S. citizens and at least one French citizen.

Nigerian President Goodluck Jonathan visited the crash site on Monday and declared three days of official mourning.

Dana Airlines is a domestic air carrier that operates a fleet of Boeing MD-83 aircraft for the hourlong flight from Abuja to Lagos.